It's surprising that a number of Smash Bros. amiibo figures are still relatively rare, depending on where you live. Some figures that are as common as rainy days here in the UK require pre-orders in the US, even when they were originally released in 2014 / 2015.
That seems to be the case with some figures up for pre-order from Best Buy in the US. The amiibo Alerts Twitter account has posted links for four amiibo that can be ordered for delivery on 14th October; they're all restocks of popular (and in some instances rare) figures:
Pre-orders were still live at the time of publication, but you should move fast if you're in the US and want to grab these figures.
amiibo Alerts has pointed out two more rare amiibo that are now available to pre-order, both also due on 14th October.
With thanks to Spoony-Tech for the heads up.